Telephone ringing system



Nov. 4, 1941. c. w. HALLIGAN TELEPHONE RINGING- SYSTEM Filed April 24,1940 .2 Sheets-Sheet 1 I INVENTORY B CJWHALL/GAN y 1 v A A 7' TORNE VPatented Nov. 4, 1941 UiTED STATES orrice TELEPHONE RINGING SYSTEMApplication April 24, 1940, Serial No. 331,296

19 Claims. (01. 1'79'-86) This invention relates to full selectiveringing telephone systems and more particularly to systems of thecharacter disclosed in U. S. Patent 2,088,311, issued to L. J. Stacy onJuly 27, 1937, in which gas-filled tubes are employed and so arrangedthat any one of a plurality of four stations can be selectively calledto the exclusion of all the others, when alternating currentsuperimposed on a direct current source, is applied to the line in apredetermined manner,

An object of the invention is to selectively operate any one of morethan four electromagnetic devices associated with a two-conductor lineto the exclusion of the others.

A feature of the invention resides in the provision of such signalingsource component voltages, both alternating and direct current, andmeans for their selective application to a line and ground, in eitherpolar direction and in so connecting an electromagnetic device andgasfilled discharge tube to the line and ground at each station, inassociation with suitable impedance elements, that the selectiveapplication to the line of such signaling current will cause theselective response of a desired particular one of said connected devicesto the exclusion of all the others.

The invention will be understood from the following description andaccompanying drawings in which:

E, F, G and H are shown on theline L, at each of which is located a,ringer R and a three-element gas-filled dischargetube T, and indicatedas AR, AT, BR and BT, etc. The ringer ARa-t station A is connectedbetween the ring conductor series with current-limiting resistance 4C.At

Fig. 1 represents a line having eight stations connected thereto;

Fig. 2 represents a portion of an operators cord circuit arranged toselectively connect ringing current to the line of Fig. 1 in diiierentmanners .3

Fig. 3 in twelve different manners to selectively operate the stationringers connected thereto;

Fig. 4A is a schematic representation of the different manners in whichringing current is connected by the cord circuit of Fig. 4; and

Fig. 5 is a four-element gas-filled discharge tube of the type describedin a copending application, filed April 24, 1940 in the name of W. H. T.Holden, Ser. No. 331,270,.emp1oyed at certain of the stations of theline shown in Fig. 3.

Referring to Fig. 1 eight stations, A, B, C, D,

this station, however, the anode of tube CT is connected to the ringconductor 1 in series with the ringer, i. e., connected between theringer and condenser 3C as shown. I

At stations B and D the ring conductor is grounded through seriallyconnected resistances and condensers 2B and 3B and 2D and 3D,respectively. The control gaps at both stations are connected across therespective condensers 3B and 3D. At station E the anode'is connected toground in series with the ringer BR and at station D the anode isconnected to the ring conductor of the line in series with thecorresponding ringer DR.

At stations E and G the respective ringers are connected between the tipconductor 5 of the line at ground in series with the respectiveresistances and condensers 2E, 3E and 2G and 3G. The control gaps of thetubes at these stations are connected across the respective resistances2E and 2G. At station E the anode is connected to ground, and at stationG the anode is connected to the tip conductor 5' of the line in serieswith the respective ringer GR.

At stations F and Hthe connection arrangements are the same as forstations B and D previously described except that the connections I areto the tip conductor 5 of the line instead of the ring conductor I, i.e., the control gaps are connected across the respective condensers 3Fand 3H, the anode of the tube at station F is connected to groundthrough the ringer and at station H the anode is connected in serieswith the ringer to the tip of the line and the opposing electrode, 1.e., the cathode is connected to ground.

Now referring to the cord circuit of Fig, 2

eight selective ringing keys KA, KB, KC, etc. are

shown each so connected as to apply either of the two superimposedringing current sources SI or S2 to the line in a different one of fourmanners. Source SI comprises an alternating current ringing generator 6of comparatively low voltage and a direct current source I of relativelyhigh voltage and source S2 comprises an alternating current ringinggenerator H of a relatively higher voltage than generator 6 and a directcurrent source 9 of relatively lower voltage. In practice the lowvoltage alternating source 6 may be of the order of 45 to 50 volts, thehigh voltage alternating current source 8 of the order of 90 volts, thelow voltage direct current source of the order of 45 to 50 volts, andthe high voltage direct current source of the order of 100 to 110 volts,the controlling requirement being that when source S l comprising a highvoltage direct current component, and a low voltage alternating currentcomponent is applied between either side of the line and ground, thedirect current voltage shall produce such a potential drop across thecondensers connected to that side of the line as to fire the controlgaps of the tubes connected acrossv them, whilethe alternating currentcomponent shall n'otcause a sufiicient potential drop across thecorresponding resistances to fire the control gaps connectedthereacross.

Conversely when source S2 comprising a high voltage alternating, currentcomponent and a low voltage dithe line to fire the control gaps ofthetubes connected thereacross andthe direct current components shallnot be high enough to efiect a voltage drop across the correspondingcondenser to ffire ,the tubes with control gaps connected in bridgethereto.

Insertion of plug in in jack H and operation of key KA, for example,efiects connection of the source S2 to the line in a mannerdiagrammatically shown at A of Fig. 2A, i. e., the tip conductor of theline is grounded and negative superimposed". current is connected to thering conductor I. Source S2, as before mentioned, comprises a highvoltage alternating current source 8 (of the order of 90 volts) and thisvoltage when applied to the ring conductorof the line will cause acontrol gap discharge at those stations connected to the ring conductorwhose gaps are connected across a resistance, 1. e.,, at stations A andC. The tubes at stations B and D have their control gaps connectedacross condensers 3B and 3D, respectively, and as the direct currentcomponentvoltage of source S2 does not cause a high enough potentialdrop across these condensers, the control gaps at these stations do notbreak down. Stations E, F, G and H have their tubes and ringersconnected to the tip con- 'ductor 5 and therefore no control gapbreakdown occurs at anylof these stations.

'At station A tube AT becomes ionized by the control gap discharge anddue to the fact that negative superimposed current is present on thering conductor vI of the line a main gap dis- ,charge occurs and currentflows from the grounded anode to the cathode, through the ringer AR,

conductor l. of the line, and thence to the negative poleof the directcurrent component of source S2 in sufficient volume to cause the ringerto respond.

At station C the anode of tube CT is connected in a reverse direction tothat of the anode at station A and as the main gaps of the tubesemployed are substantially rectifying, i. e., current will flow inappreciable amounts only in the direction of the anode to the cathode,no main gap discharge will take place at station C and the ringer CRwill be unaffected.

Operation of key KC also connects source S2 to the ring conductor I ofthe line but reverses the polarity of the direct current component, i.e., key KC connects positive pulsating current to the line. At stationsA and C the respective tube control gaps break down as before but, asthe efi'ective'impedance of the current pulsations are in a positivedirection the main gap of tube CT breaks down to cause ringer CR tooperate whereas the reverse connection of the main gap at station Aprevents such a discharge through the tube.

Operation of key KB connects source SI in a negative direction to thering conductor I of the line. As before explained the direct currentcomponent of this source (SI) is of the order of volts which issufficient to impress a control gap breakdown potential across thecondenser at all four stations connected to the ring conductor, i. e.,stations A, B, C and D. Only stations B and D, on the ring side of theline, however, have their two control gaps connected across condensersand therefore only these tubes will ionize. The tube anode at station Bis connected to ground through the ringer BR and the cathode of the maingap is connected to the ring conductor of the line. Hence this gap willbreak down on the peak potential of the pulsating source S! andsunicient current will flow in the ringer coils to cause its operation.

In a similar manner, actuation of key KD will connect source SI in thepositive direction to the ring conductor and ground the tip. The controlgaps of tubes BT and DT will fire as in the case when key KB wasactuated but, as the polarity of pulsating current connected to the lineis positive instead of negative with respect to ground, only the maingap of the tube at station D will pass current sufiicient to operate theringer.

It will be noted that the connection of stations E, F, G and H areidentical with stations A, B, C and D, respectively, except for thedifference that these four stations are connected to the tip of the lineinstead of the ring and that keys KE, KF, KG and KH are arranged toconnect the current sources SI and S2 to the tip conductor 5 of the linein exactly the same manner as the respective keys KA to KD are arrangedto connect to the same sources to the ring conductor. Therefore, theselective operation of any one of the eight keys KA, etc. will cause theselective operation of a particular one of said stations A, B, etc. tothe exclusion of the others.

The fundamental characteristics of the present invention, as exemplifiedin the foregoing description, resides in the use of circuit arrangementsfor firing, i. e., breaking down, the control gaps of the gas-filledtubes employed at the station, certain of which circuit arrangements aresensitive to alternating currents only and others of which are sensitiveto direct current only and in the provision of such superimposedalternating and direct ringing current supply sources that one sourcewill have a suihciently high alternating current voltage component tofire those tubes-at 'thestation whosecircui-ts are sensitive toalternating current only and another source which will have a directcurrent component voltage sufliciently high to fire those tubes whosecircuits are sensitive to direct current.

In the arrangement shown in Figs. 1, 2 and 2A, a combination ofalternating and direct current is applied in all cases to the controlgap circuit of the tube and considerable care is therefore necessary toso choose the component voltages of the ringing sources and to so adjustthe control gap circuit arrangement that the proper margin of operationand non-operation at the different stations are maintained.

An alternative, and in some respects more preferable arrangement, is toarrange the connection so that either alternating current alone ordirect current alone is applied to the control gap circuits of the tube,while at the same time applying combined alternating current and directcurrent superimposed one on the other, to the main gap. Such anarrangement which necessitates the use at certain of the stations of aslightly different tube structure, having four instead of threeelectrodes, is shown in Figs. 3, 4, 4A and 5, which latter figure showsa tube having the same anode-cathode structure as the conventionalthree-element tube now in use, but in which two independent closelyspaced electrodes are provided which constitute the control gap.

Referring more specifically to Fig. 5, a gasfilled discharge tube ofconventional size and shape is shown having two half disc electrodes 5|and 52 supported in the base in any convenient manner and coated withsome well-known electron emitting or activating substance. Extendingupwardly through the center of the tube and suitably insulated from theelectrodes 5| and 52 is the usual uncoated wire electrode 53 which formsthe anode of the device. Due to the small area of the uncoated free endof anode 53 and the coated electrodes 51 and 52, the gap therebetweenhas a substantially rectifying characteristic and requires a relativelyhigh cold breakdown potential. In the circuit of the present invention,wherein tubes of the character shown in Fig. 5 are used, the half discelectrodes 5| and 52 may be permanently connected together to form asingle electrode as shown by the connection 55, which connectedelectrodes now become one cathode element of the main gap of which theelectrode 53 is the anode. Also supported within the tube and suitablyinsulated from the electrodes 5|, 52 and 53, as well as from each otherare two other wire electrodes 54 and 55 whose upper extremities arecoated with some activating substance and closely positioned withrespect to each other to provide a short discharge gap and asubstantially bilateral discharge characteristic of a low breakdownpotential, i. e. of the order of '70 volts. These two electrodes providea control gap for the tube which is independent of the main gap whichexists between electrodes 53 and 5!, 52.

Now referring to Figs. 3 and 4, which show a full selectivetwelve-station line made possible by the use of tubes constructed inaccordance with Fig. 5, and a cord circuit having means for selectivelyringing any one of the connected stations on the line to the exclusionof the others, which cord circuit means employs two pulsating orsuperimposed ringing current sources similar in all respects to thesources S1 and S2 previously escribed and shown in Fig. 2. The manner inwhich the components of these two sources are connected to the line ofFig. 3 to effect selective operation of the station ringers thereon isshown in Fig. 4A.

It will be noted that in Fig. 3, thefirst eight stations A, B, C, D, E,F, G and H have their control gaps fired by potentials connected inbridge of the line in contradistinction to the arrangement of Fig. 1 inwhich the control gaps are fired by potentials connected between oneside or the other of the line and ground. At the last four stations I,J, K and L, the control gaps are fired by potentials of the propercharacteristics connected between one side of the line and ground andthe corresponding main gaps are discharged in a circuit between theopposite side of the line and ground.

Stations A, C, E, G, J and L are the so-called negative stations, i. e.,station ringers respond to negative superimposed pulsating current andemploy conventional three-element discharge tubes whereas stations B, D,F, H, I and K which are the so-called positive stations, i. e., stationswhose ringers respond to positive pulsating current, employ four-elementtubes of the type previously described and shown in Fig. 5.

In Fig. 4, as in Fig. 2, two sources of signaling current S1 and S2 areprovided, source S1 comprising a high voltage source I of direct currentand a lower voltage source 6 of alternating ringing current and sourceS2 comprising a high voltage source of alternating current and a lowervoltage source of direct current. In practice the potentials ofthe'different components of sources S1 and S2 are the same as previouslygiven for- Fig. 2.

The operation of Figs. 3 and 4 will now be described:

Assuming that station A (Fig. 3) is to be signaled, the operator willactuate key KA of the cord circuit (Fig. 4) thereby connecting source S2to the line and ground in the manner shown A of Fig. 4A, i. e., the highvoltage alternating current component of the source is connected inbridge of the line by way of plug l0 and jack H and the negative pole ofthe low voltage direct current component 9 is connected to the tip ofthe line and the positive pole grounded, the eifect of this being toconnect the high voltage component of the source alone in bridge of theline and to connect negative superimposed'pulsating current to the ringconductor. At station A of the line (Fig. 3) a bridge exists across theline which comprises condenser 3A, resistance 2A, and ringer AB inseries. Connected across resistance 2A is the control gap of the tubeAT. The value of resistance 2A is so chosen that the high voltage ofgenerator 8 (of the order of 90 volts) causes the voltage dropthereacross sufiicient to fire this gap (i. e. of the order of volts)thus causing ionization of tube AT whereupon the negative pulsatingcurrent, connected to the ring conductor of the line causes a main gapdischarge to take place in tube AT in the direction of the anode tocathode and through the ringer AR thereby causing this ringer to beactuated.

At stations B, C, D, E, F, G and H, a bridge circuit also across theline which bridge, in each instance, comprises a resistance. 2 and acondenser 3 and therefore application of the high voltage alternatingcurrent across the line at the central office causes the potential dropacross the resistance element of the bridges of each of the stations,which is of the order of '70 volts. At stations B, C and D, therespective tube control gap will break down and cause ionization withinthe tubes due to the fact that their control gaps are connected acrossthe respective resistances at whose terminals a control gap potentialexists.

At stations E, F, G and H,however, the tube control gaps thereat areconnected across the respective condensers 3 which condensers offer acomparatively low impedance to the alternating current connected tothemand therefore will not cause a sufficient potential drop to firethese tubes. a

Although the tubes at stations B, C and D are ionized by a control gapbreakdown, no main gap discharge, or only a relatively small su'chdischarge takes place due to the manner in which the respective'anodesand cathodes are connected with respect to the line. At station B themain gap will. only conduct in a positive direction to the ring of theline through the ringer and across the anode-cathode gap to ground andas the ring conductor of the line in the present instance is negative,the ringer BR at station B will be unaffected. At stations C and D themain gap connections are to the tip of the line instead of the ring asat stations A and B and hence in view of the fact that the pulsatingcurrent is applied to the ring conductor no main gap discharge occurs atthese stations. The low voltage direct current source 9 is not ofsufiicient potential to afiect the main gaps at stations C and D.

At stations I, J, K and L, the control gap breakdown potential isderived from a voltage drop across an impedance connection between thetip of the line and ground and hence ionization of the tubes inthesestations is not effected, since source 9 is of insufiicient potentialfor the ionization of these tubes.

If station F is to be signaled, key KF will be operated connecting thehigh voltage direct current component 1 of source S1 across the linesary. At this station the tube ST has its control gap connected acrosscondenser 3F in series with the current limiting resistance 4F. Due tothe fact that a high direct current voltage is impressed across the lineat the central ofiice, the condenser is charged to a potential which issufficiently high to cause the control gap to break down and ionize thetube. The anode of the main gap is connected to the ring'conductor ofthe line and the opposing or cathode electrode is connected in serieswith the ringer to ground by which method of connection, positivepulsating current on the ring will flow across the main gap to groundthrough the ringer to cause its actuation.

It will be obvious without further description that none of the otherringers will respond, either due to the fact that their correspondingtubes are not ionized or due to the fact that the direction of thesuperimposed pulsating current is either in the wrong direction orconnected to the wrong side of the line to cause the main gap discharge.

As before pointed out stations I, J, K and L have their control gapsconnected between the tip of the line and ground and the main gapbetween the ring of the line and ground and hence superimposed pulsatingcurrent connected between the ring of the line and ground will not causea control gap discharge. Likewise'the low voltage source 6 is ofinsufficient potential to cause a control gap discharge at thesestations.

Operation of keys KC and KD connect superimposed current having a highvoltage alternating current component between the tip of the line andground and hence control gaps at stations I and J will break down andoperation of keys KG and KH connect superimposed current having a highdirect current component in a similar manner thereby breaking down thecontrol gaps at stations K and L, but due to the fact that the main gapsare connected to the ring of the line, no discharge thereacross occurs.

It may be mentioned that although a line has been shown employing boththree and four-element tubes, in practice it may be found desirable tomaintain uniformity of apparatus and therefore to equip each stationwith four-element tubes which will be connected in an obvious manner.

It will also be obvious that although the present invention has beendescribed as a selective ringing telephone system, any suitable type ofelectromagnetic device other than a ringer, as for example a relay, canbe employed and selectively operated in the same manner.

What is claimed is:

1. In a party line telephone system, means for selectively ringing anyone of twelve stations on a line comprising a polarized ringer and agasfilled tube at each station, two sources of different voltagealternating current, and two sources of different voltage directcurrent.

2. In a multiparty selective ringing telephone system, a line, aplurality of stations thereon, a gas-filled discharge device havingcontrol and main discharge gaps at each station, a ringer in series witheach main gap between ground and one side of the line, a condenser and aresistance in a series bridge across the line at certain of saidstations, and in series from one side of the line to ground at certainother stations, connections at certain ofsaid stations shunting thecontrol gap of the discharge device thereat across the respectiveresistance and at other stations across th respective condenser, twodifferent voltage sources of alternating current and two differentvoltage sources of direct current and means for selectively connectingthe higher voltage current source of either characteristic and the lowervoltage source of the other characteristic inseries and in either polardirection between ground and either side of the line and the highvoltage source alone either across the line or between ground and oneside of the line, the values of said resistances, condensers andvoltages being so chosen that a control gap discharge will take place inthose devices whose control gaps are shunting a resistance when thealternating current applied is higher than the direct current and inthose devices whose control gaps are shunting a condenser when thedirect current voltage applied is higher than the alternating current.

3. In a multiparty selective ringing telephone system employinggas-filled discharge tubes and polarized ringers at the stations, aline, a ringer and a gas-filled tube at each station, two differentvoltage sources of alternating current and two different voltage sourcesof direct current, a selective switch for simultaneously associatingeither the high voltage alternating current and low voltage directcurrent or the low voltage alternating current and high voltage directcurrent with the line and ground in a plurality of differdifferentmanners, the higher voltage alternatingcurrent source and the lowervoltage direct current source, or the lower voltage alternating currentsource and the higher voltage direct current source to the line andground, a gas-filled discharge tube having main and control gaps at eachstation, and means at each station associating the respective tubes andringers with the line and ground in such a manner that the connection tothe line of the higher voltage alternating current source and lowervoltage direct current source, in a particular one of said manners willcause selective actuation of the ringer at a predetermined station, andconnection of the higher voltage direct current source and lower voltagealternating current source in another one of said same manners willcause selective actuation of a ringer at another station.

5. A selective ringing telephone system for party lines having morethan. four stations and employing polarized ringers and gas-filled tubesat the stations characterized by two difierent sources of superimposedringing current, on source having an alternating current component of avoltage higher than the control gap breakdown Voltage of the tubesemployed and a direct a current component of a voltage less than saidcontrol gap breakdown voltage and said other source having a directcurrent component of a voltage higher than said control gap breakdownvoltage and an alternating current component of a lower potential thansaid breakdown voltage, and means for selectively applying either ofsaid sources to the line in a plurality of different manners.

6. In a selective ringing party line telephone system employingpolarized ringers at each station on the line, two sources of difierentvoltage direct current and two sources of different voltage alternatingcurrent, means for selectively and simultaneously connecting either thehigher voltage alternating current and lower voltage direct lectiveactuation of a predetermined one of said ringers to the exclusion of theothers. Y

8. In a selective signaling system, a line, a plurality ofelectromagnetic devices, two sources of composite signaling current, onesource comprising a high voltage alternating current component and alower voltage direct current component and the other source comprising ahigh voltage direct current component and a lower voltage alternatingcurrent component, a gas-filled discharge tube connecting eachelectromagnetic device to one side of the line, and switching means forselectively connecting either source to the line in such a manner thatthe higher voltage component of the applied source is connected in onemanner and both components in series are connected in a difierent mannerto selectively operate a particular one of said devices to the exclusionof the others.

9; In a multiparty selective ringing telephone system, a line, aplurality of stations thereon, a gas-filled discharge device, having acontrol and a main discharge gap, at each station, a ringer in serieswith each main gap between groundand one side of the line, a condenserand resistance serially connected in bridge of the line at certain ofsaid stations and from one side of the line to ground at certain otherstations, connections at certain of said stations shunting the controlgap thereat across the respective resistance and at other stationsacross the respective condenser, two sources of difierent voltagealternating current and two sources of different voltage direct current,and means for selectively and simultaneously connecting the high voltagesource of either characteristic and the low voltage source of the othercharacteristic to the line and ground in such different manners that anyone of twelve ringers connected to the line can be selectively actuatedto the exclusion of eleven others.

10. In a twelve-party selective ringing telephone system, a line, aplurality of polarized ringers associated therewith and means forselectively actuating any one of twelve of said ringers to the exclusionof eleven others, said means comprisingtwo sources of different voltagealternating current and two sources of different voltage direct currentselectively connected to said'line and ground in difierent manner.

current or the higher voltage direct current and lower voltagealternating current to the line and ground in a plurality of diiferentmanners and means for connecting the station ringers to the line andground in such different manners that a single and difierent ringer willrespond to each selective connection of said current sources.

7. In a multiparty selective ringing telephone system, a line, aplurality of polarized ringers associated therewith, two sources ofdifferent voltage alternating current, two sources of diiierent voltagedirect current, means for selectively and simultaneously connectingeither the high voltage alternating current source and the lower voltagedirect current source or the higher voltage direct current source andthe lower voltage alternating current source to the line and ground indifferent predetermined manners, and means comprising a gas-filleddischarge device associating each ringer with the line and ground insuch different manners that the connection of said current sources tothe line and ground in any one of said different manners will cause se-11. In a selective ringing party line telephone system employing apolarized ringer at each station, means for selectively actuating anyone of twelve ringers on the line to the exclusion of eleven others,said means comprising two different voltage sources of direct currentand two different voltage sources of alternating current, a switchingdevice for selectively and simultaneously connecting the higher voltagedirect current source and the lower voltage alternating current sourceor the higher voltage alternating current source and lower voltagedirect current source to the line and ground in differentmanner and agas-filled discharge tube at each station, each tube being connected tothe line associated ringer and ground in such a difierent manner thateach ringer will respond to a different selective connection to the lineof said current sources.

12. In a twelve-party selective ringing telephone system, a line, aplurality of stations thereon, a ringer and a gas-filled dischargedevice connected to said line and ground at each station in differentmanners and means for selectively actuating any one of twelve ringersconnected to said line to the exclusion of eleven others, said meanscomprising two different voltage sources of I alternating current andtwo difierent voltage sources of direct current, and a switching devicefor selectively and simultaneously connecting the higher voltage sourceof either characteristic and the lower voltage source of the othercharacteristic to the line and ground in six different manners.

13. In a multiparty selective ringing telephone system, a line, twelvestations thereon, a ringer and a gas-filled discharge device at eachstation, a source of direct current and a source of alternating currenteach having a peak voltage higher than the potential required to firethe control gap of the discharge device, another source of directdifferent manners that the selective connection of said sources to theline and ground in any one of said six manners will cause the selectiveactuation ofthe ringer at a particular one of said twelve stations tothe exclusion of the others.

14. In a telephone ringing system, a line, a

plurality of polarized ringers, two sources of different voltagealternating current and two sources of different voltage direct current,means for selectively connecting said sources to the line and ground intwelve different manners, and means comprising a gas-filled tube forassociating each ringer with the line, said tubes being so constructedand individually connected to the line, respective ringer and ground,that the selective connection of said sources to the line in any onemanner will cause the selective actuation of a single one of said twelveringers to the exclusion of the other eleven.

15. In an eight-party selective ringing telephone system, a line, eightstations thereon, a

ringer at each station, two separate sources of superimposed ringingcurrent, one of said sources including a high voltage alternatingcurrent component and a relatively low voltage direct cur-' rentcomponent, and the other source including a L high voltage directcurrent component, and a relatively low Voltage alternating currentcomponent, means for selectively connecting the two components of eachsource with the line and ground in four different manners, and means ateach station, in association with the respective ringers, including agas-filled tube, so connected and arranged that the particularconnection to the line of either source in any one manner will cause theselective actuation of a particular ringer to the exclusion of all theothers.

16. In a multiparty selective ringing telephone system, a line, aplurality of subscribers stations thereon, a ringer at each station, twodifferent voltage sources of alternating current and two differentvoltage sources of direct current, means for selectively andsimultaneously connecting the higher voltage source of alternatingcurrent across the line and the lower voltage direct current source ineither polar direction to either side of the line in series with thealternating current source and ground, or the higher voltage directcurrent source across the line in either polar direction and the lowervoltage alternating current source to either side of'the line in serieswith the direct current source and ground, a three-electrode gas-filleddischarge tube at each station, and connecting means for associating therespective ringer and tube at each station with the line in such amanner that a different one, and only one, of said ringers will respondto each particular simultaneous connection to the line of alternatingand direct current.

17. In an eight-party selective ringing telephone system, a line, eightstations thereon, a first composite source of high voltage alternatingand low voltage direct current, a second composite source of low voltagealternating and high voltage direct current, means for selectivelyconnecting either composite source to the line and ground in such amanner that the components thereof are in series across the line, eitherpole of the direct current component is connected to either side of theline, and ground is connected to the side of the line opposite to thatto which the direct current component is connected, a ringer at eachstation, means including a gasfilled discharge tube at each station forassociating the respective ringer with the line in such a manner thatthe connection of either first or second sources of current in aparticular selective manner will cause the selective operation of asingle one of said ringers to the exclusion of all the others.

18. In a selective ringing telephone system, a line, a plurality ofstations thereon, a ringer at each station, two sources of superimposedpulsating ringing current one having a high voltage alternating currentcomponent and a low voltage direct current component, and the other alow voltage alternating current component and a high voltage directcurrent component, selective switching means for connecting eithersource in either polar direction across the line and for groundingeither side of the line, a ringer and a gas-filled tube having main andcontrol discharge gaps at each station, and means for associating saidringers and tubes with the line and ground in such a manner that anyselective operation of said switching means will cause the lar ringer tothe exclusion of all the others.

19. In a selective ringing telephone system,a line, eight stationsthereon, a ringer at each station, two sources of ringing current, onehaving a high voltage alternating current component and a low voltagedirect current component and the other a low voltage alternating currentcomponent and a high voltage direct current component, selectiveswitching means'for simultaneously connecting the components of eithersource with the line and ground in four different manners, a gas-filledtube at each station, each tube having control and unilateral maindischarge gaps, and means for associating said tubes and respectiveringers with the line and ground CLAIR W. HALLIGAN.

